1. Field of the Invention
The present invention relates to a coaxial type impedance matching device, in which dielectrics are housed in sliding manners in a matching device body having an external conductor and an internal conductor.
2. Description of the Related Art
A double-slug tuner disclosed in “A Communication Engineering Handbook (Maruzen Co., Ltd., 1957)” has been known as a coaxial type impedance matching device of this kind.
Here, the double-slug tuner has the following problems to be solved. In this double-slug tuner, more specifically, the impedance is matched by sliding two slugs in the matching device body. In this double-slug tuner, however, the impedance matching range retained is narrow in a range of VSWR (Voltage Standing Wave Ratio) from about 1 to 10 so that its widening is desired. On the other hand, the impedance matching range can be widened by increasing the number of slugs. However, the adoption of this construction raises a problem that the position adjustment of the slugs is seriously complicated.
Also, external connectors are connected to connectors, which are provided at an input portion and an output portion of the matching device body, so that in this double-slug tuner, the matching device body is connected to an amplifier and an antenna through coaxial cables. In this case, the contact resistances exist between an external electrode and the external conductor of the double-slug tuner. The contact resistances cause slight reduction in the gain of the double-slug tuner. It is, therefore, desired to improve the gain reduction. Moreover, the connectors and the matching device body are made separate and have to be mounted on the matching device body. This results in a rise of the cost, which is preferably lowered. In this double-slug tuner, moreover, when a signal S of a high output is inputted, a spark may occur between an internal conductor and sliding fittings attached to the slugs. It is preferable to improve this point.
Furthermore, in this double-slug tuner, the electromagnetic waves may leak from a slit formed in the external conductor. It is preferred to improve this problem.